feat(client): allow binary returns (#114)

lithic-java-core/src/main/kotlin/com/lithic/api/core/http/BinaryResponseContent.kt

@@ -0,0 +1,15 @@
+package com.lithic.api.core.http
+
+import java.io.Closeable
+import java.io.IOException
+import java.io.InputStream
+import java.io.OutputStream
+
+interface BinaryResponseContent : Closeable {
+
+    fun contentType(): String?
+
+    fun body(): InputStream
+
+    @Throws(IOException::class) fun writeTo(outputStream: OutputStream)
+}

lithic-java-core/src/main/kotlin/com/lithic/api/services/Handlers.kt

@@ -4,6 +4,7 @@ package com.lithic.api.services
 
 import com.fasterxml.jackson.databind.json.JsonMapper
 import com.fasterxml.jackson.module.kotlin.jacksonTypeRef
+import com.lithic.api.core.http.BinaryResponseContent
 import com.lithic.api.core.http.HttpResponse
 import com.lithic.api.core.http.HttpResponse.Handler
 import com.lithic.api.errors.BadRequestException
@@ -16,6 +17,8 @@ import com.lithic.api.errors.RateLimitException
 import com.lithic.api.errors.UnauthorizedException
 import com.lithic.api.errors.UnexpectedStatusCodeException
 import com.lithic.api.errors.UnprocessableEntityException
+import java.io.InputStream
+import java.io.OutputStream
 
 @JvmSynthetic internal fun emptyHandler(): Handler<Void?> = EmptyHandler
 
@@ -25,12 +28,20 @@ private object EmptyHandler : Handler<Void?> {
 
 @JvmSynthetic internal fun stringHandler(): Handler<String> = StringHandler
 
+@JvmSynthetic internal fun binaryHandler(): Handler<BinaryResponseContent> = BinaryHandler
+
 private object StringHandler : Handler<String> {
     override fun handle(response: HttpResponse): String {
         return response.body().readBytes().toString(Charsets.UTF_8)
     }
 }
 
+private object BinaryHandler : Handler<BinaryResponseContent> {
+    override fun handle(response: HttpResponse): BinaryResponseContent {
+        return BinaryResponseContentImpl(response)
+    }
+}
+
 @JvmSynthetic
 internal inline fun <reified T> jsonHandler(jsonMapper: JsonMapper): Handler<T> {
     return object : Handler<T> {
@@ -96,3 +107,24 @@ internal fun <T> Handler<T>.withErrorHandler(errorHandler: Handler<LithicError>)
         }
     }
 }
+
+class BinaryResponseContentImpl
+constructor(
+    private val response: HttpResponse,
+) : BinaryResponseContent {
+    override fun contentType(): String? {
+        return response.headers().get("Content-Type").firstOrNull()
+    }
+
+    override fun body(): InputStream {
+        return response.body()
+    }
+
+    override fun writeTo(outputStream: OutputStream) {
+        response.body().copyTo(outputStream)
+    }
+
+    override fun close() {
+        response.body().close()
+    }
+}